The big difference is on Reddit you follow the topic (subreddit). People might browse a hashtag but Twitter/Instagram/Facebook are much more centered around the person, your default stream is not based on topics but people. If you follow someone you see what they post, so it becomes much more about ego and follower count. Yes Reddit has karma but it’s much less central to things since no matter how much karma you have your new posts are in new with 1 upvote and each post has to earn visibility, whereas on Instagram if you have a million followers a million people will see it. Reddit shares some of the downsides of other social media (time wasting, pointless arguments) but it’s much more anonymous so removes one of the worst downsides of the others which is the excessive egotism and validation seeking. Also it’s much easier on Reddit to curate our political shit you want to avoid because you can avoid those subreddits whereas on other platforms you follow someone’s content but then get their fluff and politics like it or not. So I agree Reddit has some downsides but for mental health it’s the best social media option by far.